University of California at San Diego. "They
can't both be right, so the judge believes first
one witness, then the other."
The "waterfall" illusion, described by
Aristotle in the fourth century B.C., presents
ambiguity related to motion. If you stare at a
waterfall for a minute or so, then shift your
gaze to the surroundings, the new scene
appears to drift upward, opposite to the direc
tion of the falling water. The neural basis of
this phenomenon seems to be a yin-yang rela
tionship among neurons-when those fussy
for the direction of motion of the falls become
adapted or fatigued, antagonistic fellow neu
rons take over, moving the scene in the oppo
site direction.
All very academic, but in the world of air
combat, illusions can serve a more serious pur
pose. In October 1987 Air Force pilots from an
F-16 squadron at Cannon Air Force Base in
New Mexico returned from a bombing run
over other F-16s at an outlying field. Actually,
no real bombs were dropped in the training
exercise; pilots merely indicated which air
planes they had chosen to attack.
Debriefing the pilots after the raid, Capt.
RobertN. Kang, USAF, and Gregg E. Irvin of
Science Applications International Corpora
tion dropped their own bomb-nine of the
eleven pilots had attacked cloth dummies
instead of real F-16s. Asked to choose between
black-cloth silhouettes plastered on the white
tarmac and the actual jet fighters, they chose
the high-contrast cloth versions.
"The pilots wouldn't believe it," recalled
Irvin. "One of them threw his chair across the
room in anger."
The results confirmed months of labora
tory simulation at Wright-Patterson Air Force
Base near Dayton, Ohio. Using a miniature